Field of the Invention
The present invention relates to a positioning device, and more particularly to a positioning device for various types of equipment including control of the capacity of a variable displacement piston motor/pump. And, the invention also relates to a speed changing device of a rotating body using a hydraulic motor.
Today""s machines and equipment have been improved in performance such as speedup and labor saving on the basis of the employment of a hydraulic pressure. Especially, the piston motor/pump has high performance and efficiency and is important. This piston motor/pump is extensively used for construction work machines and many other fields.
The hydraulic motor includes a variable displacement motor whose capacity can be changed and a fixed displacement motor whose capacity cannot be changed.
The variable displacement motor will be described with reference to FIG. 8 to FIG. 10.
FIG. 8 shows a sectional diagram of the hydraulic motor disclosed in Japanese Patent Publication No. 4-42550. This piston motor is changed its capacity between two levels.
Specifically, first seat face 58a of swash plate 58 housed in casing 55 is contacted to inside wall surface 55a of the casing to position the capacity at a maximum capacity position. The capacity is positioned at a minimum capacity position when second seat face 58b of the swash plate 58 is contacted to the inside wall surface 55a of the casing. The positioning accuracy of the maximum capacity position and the minimum capacity position is determined depending on the accuracy of various parts such as the swash plate 58 and the casing 55.
FIG. 9 shows a sectional diagram of a hydraulic motor different from the one shown in FIG. 8. This motor is an inclined shaft type piston motor. This piston motor changes the capacity position to two levels by pivoting valve plate 46. The valve plate 46 is accommodated in casing 52. The capacity position is variable according to the pivoting of the valve plate 46. Main shaft 51 is an output shaft of the hydraulic motor. The stop position of the valve plate 46 is restricted by minimum capacity adjusting mechanism 54 and maximum capacity adjusting mechanism 53. The minimum capacity adjusting mechanism 54 comprises adjusting screw 54b mounted on the casing 52 and nut 54a for fixing the adjusting screw 54b to the casing 52. One end of the adjusting screw 54b protrudes from the inside surface of the casing 52, and the other end protrudes from the outside surface of the casing 52. The maximum capacity adjusting mechanism 53 is also formed in the same way.
The motor has the minimum capacity when the valve plate 46 comes in contact with the leading end of the adjusting screw 54b protruded from the inside surface of the casing 52. Similarly, the motor has the maximum capacity when the valve plate 46 comes in contact with the leading end of the adjusting screw 53b protruded from the inside surface of the casing 52.
The minimum capacity position is adjusted by the minimum capacity adjusting mechanism 54.
Specifically, the fixed state of the adjusting screw 54b by the nut 54a is released to adjust the screw-in amount of the adjusting screw 54b, and the adjusting screw 54b is fixed again to the casing 52 by the nut 54a. Thus, the minimum capacity position is adjusted. The maximum capacity position is also adjusted in the same way.
FIG. 10 is a sectional diagram of a conventional three-speed motor. In FIG. 10, like reference numerals are used to indicate the like components of FIG. 9, and their descriptions are omitted.
As shown in FIG. 10, first piston 110 and second piston 120 are disposed in body 44. The first piston 110 is connected to the valve plate 46. In first pressure-receiving chamber 130, the second piston 120 applies a pressure to the first piston 110. Second pressure-receiving chamber 140 applies a pressure in a direction to separate the first piston 110 and the second piston 120 from each other. Third pressure-receiving chamber 150 applies a pressure to the first piston 110 in a direction of the second piston 120.
The second piston 120 has second piston large-diameter section 120a having a large outside diameter.
Second piston restricting part is configured by the second piston large-diameter section 120a and body inside wall surface 44a with which the second piston large-diameter section 120a is contacted. Specifically, the large-diameter section 120a of the second piston 120 moves toward the first piston 110 to contact the large-diameter section 120a with the body inside wall surface 44a. Thus, the second piston 120 is stopped. The first piston 110 comes in contact with the second piston 120 whose movement is restricted, and the valve plate 46 is positioned at a middle position.
Servo valve 60 is a control valve for controlling the supply of pressure oil to the second pressure-receiving chamber 140 and the third pressure-receiving chamber 150. The pressure oil discharged from an unillustrated hydraulic pump is supplied to the servo valve 60. And, the pressure oil discharged from an unshown hydraulic pump through an unshown 2-position selector valve is supplied to the first pressure-receiving chamber 130. Switching of the valve position of the 2-position selector valve is controlled so to control the supply and stop of the pressure oil to the first pressure-receiving chamber 130. Thus, the supply of the pressure oil to the first pressure-receiving chamber 130, the second pressure-receiving chamber 140 and the third pressure-receiving chamber 150 is controlled so to switch the position of the first piston 110, namely the position of the valve plate 46, among three positions. Therefore, the capacity position of the motor is changed among three levels of minimum, middle and maximum capacity positions. But, the hydraulic motor shown in FIG. 10 is different from the one shown in FIG. 9 and does not have an adjusting mechanism for adjusting the minimum and maximum capacity positions.
The aforesaid capacity change of the variable displacement motor is used to change the speed of HST (hydrostatic transmission) vehicle.
The HST vehicle such as a bulldozer has its left and right running bodies (wheels or caterpillars) independently driven by left and right hydraulic motors respectively. In other words, the left running body of the vehicle is independently driven and changed its speed by a drive mechanism exclusively disposed for the left side Similarly, the right running body of the vehicle is independently driven and changed its speed by a drive mechanism exclusively disposed for the right side. Each drive mechanism comprises a hydraulic pump and a hydraulic motor.
When the HST vehicle is instructed to run at the same number of left and right rotations, namely to run straight, it causes a deviation from the course if the left and right motor capacities are different.
Therefore, the HST vehicle whose left and right running bodies are independently driven is demanded to have improved accuracy for the capacity control of the left and right variable displacement piston motors so to run without causing a deviation from the course when straight-ahead running is instructed.
And, it is also demanded to simplify a device for controlling the capacity of the variable displacement piston motor.
Besides, it is also said generally that the installing space for the hydraulic equipment mounted to the HST vehicle is limited. Therefore, it is demanded to decrease a mounting area of the hydraulic equipment.
But, there is not any conventional variable displacement piston motor which satisfies the aforesaid demands. Descriptions will be made as follows.
The piston motor of the aforesaid publication shown in FIG. 8 is mainly applied to a vehicle such as a hydraulic excavator requiring two speeds of high and low. The hydraulic excavator adjusts the pump capacity only and does not adjust the motor capacity when the pump capacity is adjusted in order to prevent the deviation from the course because its workability is better than adjusting the motor capacity in view of the mounted positions of the pump and the motor.
The HST vehicle often adjusts the motor only, because its workability is very poor when the pump capacity is adjusted to prevent the deviation from the course in view of the mounted positions of the pump and the motor.
When the hydraulic motor shown in FIG. 9 is applied to the HST vehicle, a difference in rotation speeds between the left and right hydraulic motors is remedied by adjusting the respective capacity positions of the left and right hydraulic motors. Therefore, a deviation from the course of the vehicle can be remedied.
But, the adjustment of the capacity position of the hydraulic motor shown in FIG. 9 is limited to two positions of minimum and maximum capacity positions. When this hydraulic motor is mounted to the HST vehicle, there is a problem of necessity to enlarge the maximum discharge capacity of the hydraulic pump for supplying the pressure oil to the hydraulic motor. This point will be described with reference to FIG. 11.
FIG. 11(a) shows the properties of a hydraulic motor (hereinafter called the xe2x80x9c2-speed motorxe2x80x9d) which changes its capacity position between two positions. In FIG. 11(a), the horizontal axis indicates the vehicle speed, and the vertical axis indicates traction (torque). The short dashed line in FIG. 11(a) indicates the property of the hydraulic motor when its capacity is adjusted to minimum capacity q Mmin, and the solid line indicates the property of the hydraulic motor when its capacity is adjusted to maximum capacity q Mmax.
Meanwhile, FIG. 11(b) shows the properties of a hydraulic motor (hereinafter called the xe2x80x9c3-speed motorxe2x80x9d) which changes its capacity position to three positions. In FIG. 11(b), the horizontal axis indicates the vehicle speed, and the vertical axis indicates traction (torque). The short dashed line in FIG. 11(b) indicates the property of the hydraulic motor when its capacity is adjusted to the minimum capacity q Mmin, the solid line indicates the property of the hydraulic motor when its capacity is adjusted to the maximum capacity q Mmax, and the alternate long and short dash line indicates the property of the hydraulic motor when its capacity is adjusted to middle capacity q Mmean. In FIGS. 11(a) and 11(b), the region between vehicle speeds V1 and V2 is a work region that work is mainly conducted. The region between vehicle speeds V2 and V3 is a running region that the vehicle mainly runs.
In FIGS. 11(a), (b), traction at a low speed (V1) becomes maximum MAX. In designing the vehicle or the motor, the maximum capacity q Mmax of the hydraulic motor is determined depending on a level of the maximum traction MAX.
The 2-speed motor shown in FIG. 11(a) needs that the vehicle speed is adjusted to the maximum vehicle speed V2 of the work region with the maximum capacity q Mmax retained.
Pump capacity Q Pmax of the hydraulic pump is determined by the following equation (2). In the following equation, it is determined that the engine speed is NE, the motor rotation speed is NM, the pump efficiency is xcex7PV, and the motor efficiency is xcex7MV.
Q Pmaxxc2x7NExc2x7xcex7PV=q Mmaxxc2x7NM/xcex7MVxe2x80x83xe2x80x83(1)
Q Pmax=(q Mmaxxc2x7NM/NE)xc2x7(1/xcex7MVxc2x7xcex7PV)xe2x80x83xe2x80x83(2)
The 3-speed motor shown in FIG. 11(b) needs the vehicle to have the maximum vehicle speed V2 of the work region with the middle capacity q Mmean retained. Pump capacity Qxe2x80x2 Pmax of the hydraulic pump is determined by the following equation (4).
Qxe2x80x2Pmaxxc2x7NExc2x7xcex7PV=q Mmeanxc2x7NM/xcex7MVxe2x80x83xe2x80x83(3)
Qxe2x80x2Pmax=(q Mmeanxc2x7NM/NE)xc2x7(1/xcex7MVxc2x7xcex7PV)xe2x80x83xe2x80x83(4)
The above equations (2) and (4) are compared as follows:
q Mmax greater than q Mmeanxe2x80x83xe2x80x83(5),
then,
Q Pmax greater than Qxe2x80x2Pmaxxe2x80x83xe2x80x83(6)
Therefore, when the 2-speed motor is used, the maximum discharge capacity of the hydraulic pump must be made larger as compared with the case of using the 3-speed motor.
Thus, when the 2-speed motor shown in FIG. 9 is mounted to the HST vehicle, there is a disadvantage that the hydraulic pump is required to have a larger maximum discharge capacity. In other words, the 2-speed motor must be designed to have a larger hydraulic pump than the 3-speed motor has.
When the conventional 3-speed hydraulic motor shown in FIG. 10 is mounted to the HST vehicle which has its left and right running bodies provided with the drive mechanisms comprising the hydraulic pump and the hydraulic motor respectively so that the left and right running bodies are independently driven, the capacity positions of the left and right hydraulic motors cannot be adjusted. Therefore, the vehicle may deviate from the course due to a difference in the number of rotations between the left and right hydraulic motors.
The first piston 110 and the second piston 120 shown in FIG. 10 have a different outside diameter. And, the same piston has a different outside diameter depending on its portions. Therefore, the first piston 110 and the second piston 120 have a complex structure. Besides, the body 44 for accommodating the pistons 110, 120 has a complex structure.
It is easy to apply the adjusting mechanism of FIG. 9 to the technique of FIG. 10. But, the adjustment cannot be made at the middle capacity position. Therefore, there is still a problem that a deviation from the course is caused when the vehicle goes straight at the middle capacity position.
Therefore, it is a first object of the present invention to provide a positioning device which has a simple structure and can adjust at all three positions and a motor/pump using this positioning device.
And, it is a second object of the invention to provide a speed changing device for left and right rotating bodies using a hydraulic motor which can remedy a difference in the number of rotations between the left and right rotating bodies when the rotation speeds of the left and right rotating bodies are changed among three levels.
As described above, when the 2-speed motor is used in order to obtain the same maximum vehicle speed V2, it is necessary to increase the maximum discharge amount of the hydraulic pump and to enlarge the size of the hydraulic pump as compared with the case of using the 3-speed motor. This tendency becomes more conspicuous when the number of changes of the hydraulic motor speed is increased to more multiple levels. Therefore, when the number of speed changes of the hydraulic motor is increased to three levels or more, the maximum discharge amount of the hydraulic pump can be made smaller and the size of the hydraulic pump can be decreased as compared with a case that the 2-speed motor is used. In other words, when the positioning number of the positioning device is increased to three or more, the size of the hydraulic equipment such as the hydraulic pump can be made smaller as compared with a case that the positioning device having the positioning number two is used.
But, the structures of the positioning device and hydraulic motor and the control become complex because the position of the first piston 110 is continuously changed by the servo valve 60 according to the prior art of FIG. 10. The prior art of FIG. 10 is a technique to position the rotation speed of the hydraulic motor at three positions by the positioning device. And, there was not a technology that the rotation speed of the hydraulic motor is positioned at four levels or more by the positioning device.
It is a third object of the present invention to make positioning at three positions or more by a simple structure and simple control without using the complex structure such as a servo valve and control and to change the rotation speed of the hydraulic motor to three levels or more.
In order to achieve the first object of the invention, a first invention of the present invention comprises:
a first piston (11) and a second piston (12) in a body (44), the first piston (11) having a position restricted by the body (44) and a position corresponding to the position of the second piston (12) as stop positions, and the second piston (12) having a position restricted by the body (44) and a position restricted by second piston restricting part (40b) as stop positions;
a middle position adjusting mechanism (40) for adjusting the stop position of the second piston (12) restricted by the second piston restricting part (40b);
a first pressure chamber (13) for applying a pressure to the second piston (12) in a direction of the first piston (11);
a second pressure chamber (14) for applying a pressure in a direction to separate the first piston (11) and the second piston (12) from each other; and
a third pressure chamber (15) for applying a pressure to the first piston (11) in a direction of the second piston (12).
The first invention will be described with reference to FIG. 1, FIG. 2 and FIG. 3.
The body 44 is provided with the first piston 11 and the second piston 12. The first piston 11 stops at the position restricted by the body 44 and the position corresponding to the position of the second piston 12. The second piston 12 stops at the position restricted by the body 44 and the position restricted by the second piston restricting part 40b. The first pressure chamber 13 applies a pressure to the second piston 12 in a direction of the first piston 11. The second pressure chamber 14 applies a pressure in a direction to separate the first piston 11 and the second piston 12 from each other. The third pressure chamber 15 applies a pressure to the first piston 11 in a direction of the second piston 12. And, the supply of the pressure oil to the first, second and third pressure-receiving chambers 13, 14 and 15 is controlled, so that the first piston 11 is positioned at the middle position to come in contact with the second piston 12 whose movement is restricted by the second piston restricting part 40b. This state is shown in FIG. 2.
And, the restriction position of the second piston 12 by the second piston restricting part 40b is adjusted by the middle position adjusting mechanism 40. Therefore, the stop position of the first piston 11 at the middle position can be adjusted.
The second invention comprises:
first piston (11) and second piston (12) in body (44), the first piston (11) and the second piston (12) having the same outside diameter, the first piston (11) having a position restricted by the body (44) and a position corresponding to the position of the second piston (12) as stop positions, and the second piston (12) having a position restricted by the body (44) and a position restricted by the second piston restricting part (40b) as stop positions;
a first pressure chamber (13) for applying a pressure to the second piston (12) in a direction of the first piston (11);
a second pressure chamber (14) for applying a pressure in a direction to separate the first piston (11) and the second piston (12) from each other; and
a third pressure chamber (15) for applying a pressure to the first piston (11) in a direction of the second piston (12), wherein:
the first and second pistons (11, 12) are positioned according to a difference in pressure-receiving areas to which the pressures of the first, second and third pressure chambers (13, 14, 15) are applied.
The second invention will be described with reference to FIG. 1, FIG. 2 and FIG. 3.
The body 44 is provided with the first piston 11 and the second piston 12. The first piston 11 stops at the position restricted by the body 44 and the position corresponding to the position of the second piston 12. The second stop piston 12 stops at the position restricted by the body 44 and the position restricted by the second piston restricting part 40b. The first pressure chamber 13 applies a pressure to the second piston 12 in a direction of the first piston 11. The second pressure chamber 14 applies a pressure to the first piston 11 in a direction to separate the first piston 11 and the second piston 12 from each other. The third pressure chamber 15 applies a pressure to the first piston 11 in a direction of the second piston 12. And, the supply of the pressure oil to the first, second and third pressure-receiving chambers 13, 14 and 15 is controlled to position the first piston 11 at the maximum position away from the second piston 12. This state is shown in FIG. 1. The first piston 11 is positioned at the middle position to come in contact with the second piston 12 whose movement is restricted by the second piston restricting part 40b. This state is shown in FIG. 2. And, the first piston 11 is positioned at the minimum position to come in contact with the second piston 12 whose movement is not restricted by the second piston restricting part 40b. This state is shown in FIG. 3.
The first piston 11 and the second piston 12 are designed to have the same outside diameter. The first piston 11 is positioned at the maximum, middle or minimum position depending on pressure-receiving area differences ((S2xe2x88x92S3), (S1xe2x88x92S3)) among area S1 of pressure-receiving surface 12b of the second piston 12 to which the pressure oil of the first pressure chamber 13 is applied, area S2 of pressure-receiving surface 11a of the first piston 11 to which the pressure oil of the second pressure chamber 14 is applied and area S3 of pressure-receiving surface 11b of the first piston 11 to which the pressure oil of the third pressure chamber 15 is applied.
According to the second invention, because the first piston 11 and the second piston 12 are designed to have the same outside diameter, the first piston 11 and the second piston 12 can be formed to have a simple structure, and hole 70 for accommodating these pistons 11, 12 can be configured to have a simple structure with the same diameter along any parts of the hole 70. Therefore, there are obtained effects such as facilitation of a process to produce the positioning device.
A third invention relates to the first and second inventions wherein the first piston (11) is connected to a capacity control member of the variable displacement piston motor/pump to control a capacity position of the variable displacement piston motor/pump.
The third invention will be described with reference to FIG. 4, FIG. 5 and FIG. 6.
According to the third invention, the first piston 11 is connected to valve plate 46 of the variable displacement piston motor (pump). When the first piston 11 is positioned, the valve plate 46 is positioned at the corresponding position, and the capacity position of the variable displacement piston motor (pump) is positioned.
Accordingly, the hydraulic motor of the third invention can adjust the middle capacity position. Therefore, when two hydraulic motors are used, a difference of the number of rotations between the left and right hydraulic motors can be eliminated when the hydraulic motors are changed their speeds to the middle capacity position. Thus, a deviation from the course when running straight can be prevented. Besides, according to the third invention, the hydraulic pumps can be designed to have a small capacity and can be made small in size because the capacity position is changed among three levels of the minimum capacity position, the maximum capacity position and the middle capacity position. Accordingly, the hydraulic equipment can be installed in a limited space.
According to the third invention, because the first piston 11 and the second piston 12 are designed to have the same outside diameter, they can be made to have a simple structure, and hole 70 for accommodating these pistons 11, 12 can be formed to have a simple structure having the same diameter at any part of it. Accordingly, there are obtained effects such as facilitation of a process to produce the positioning device.
A fourth invention relates to the first and second inventions, wherein the first piston (11) is connected to a capacity control member of the variable displacement piston motor/pump to control a capacity of the variable displacement piston motor/pump, and wherein the capacity controller comprises adjusting means (54) for adjusting a minimum capacity of the variable displacement piston motor/pump.
The fourth invention will be described with reference to FIG. 4, FIG. 5 and FIG. 6.
According to the fourth invention, the first piston 11 is connected to valve plate 46 of the variable displacement piston motor (pump). After the first piston 11 is positioned, the valve plate 46 is positioned at the corresponding position, and the capacity position of the variable displacement piston motor (pump) is positioned.
And, the movement of the first piston 11 which is moved to the minimum capacity position is restricted by the minimum capacity position restricting means 54b. The restricting position of the first piston 11 is adjusted by the adjusting means 54.
Thus, the hydraulic motor of the fourth invention can adjust the middle capacity position. Besides, according to the fourth invention, the capacity of the hydraulic pump can be made small and the hydraulic pump can be made small accordingly, because the capacity position is changed in three levels of the minimum capacity position, the maximum capacity position and the middle capacity position. Therefore, the hydraulic equipment can be installed in a limited space.
According to the fourth invention, because the first piston 11 and the second piston 12 are designed to have the same outside diameter, they can be made to have a simple structure, and hole 70 for accommodating these pistons 11, 12 can be formed to have a simple structure having the same diameter at any part of it. Accordingly, there are obtained effects such as facilitation of a process to produce the positioning device.
Besides, according to the fourth invention, the position of the first piston 11 which is positioned at the minimum capacity position is adjusted. The minimum capacity position is susceptible to the hydraulic motor (pump). According to the fourth invention, the minimum capacity position which is largely different and variable among individuals can be adjusted readily.
To achieve the second object, a fifth invention is a speed changing device of rotating bodies using hydraulic motors, comprising left and right variable displacement hydraulic motors (9), (9xe2x80x2) which are respectively installed for left and right rotating bodies and drive to rotate the left and right rotating bodies; hydraulic pumps (3), (3xe2x80x2) which respectively supply pressure oil to the left and right hydraulic motors (9), (9xe2x80x2); and speed switching means which changes rotation speeds of the left and right rotating bodies among three levels of rotation speeds by switching capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2), among three capacity positions, wherein:
adjusting means is provided for adjusting so that the rotation speeds of the left and right rotating bodies are made identical for each of the three levels of rotation speeds of the left and right rotating bodies.
The fifth invention will be described with reference to FIG. 1 and FIG. 13.
When the capacity positions of the left and right variable displacement hydraulic motors 9, 9xe2x80x2 are switched to the minimum capacity position, the rotation speeds of the left and right rotating bodies 100, 100xe2x80x2 are switched to the maximum rotation speed. At this point, the hydraulic motors 9, 9xe2x80x2 are adjusted to have the same minimum capacity position by the adjusting means 54. Thus, the left and right rotating bodies 100, 100xe2x80x2 have the same rotation speed.
When the capacity positions of the left and right variable displacement hydraulic motors 9, 9xe2x80x2 are switched to the middle capacity position, the rotation speeds of the left and right rotating bodies 100, 100xe2x80x2 are switched to the middle rotation speed. At this point, the left and right hydraulic motors 9, 9xe2x80x2 are adjusted to have the same middle capacity position by the adjusting means 40. Thus, the left and right rotating bodies 100, 100xe2x80x2 have the same rotation speed.
When the capacity positions of the left and right variable displacement hydraulic motors 9, 9xe2x80x2 are switched to the maximum capacity position, the rotation speeds of the left and right rotating bodies 100, 100xe2x80x2 are switched to the minimum rotation speed. At this point, the left and right hydraulic motors 9, 9xe2x80x2 are adjusted to have the same maximum capacity position by the adjusting means 53. Thus, the left and right rotating bodies 100, 100xe2x80x2 have the same rotation speed.
According to the fifth invention, when the rotation speeds of the left and right rotating bodies 100, 100xe2x80x2 are switched among the three levels by the hydraulic motors 9, 9xe2x80x2, a difference of the number of rotations between the left and right rotating bodies 100, 100xe2x80x2 can be eliminated.
Besides, according to the fifth invention, the capacity of the hydraulic pump can be made small, and the hydraulic pump can be made small in size because the capacity positions of the left and right variable displacement hydraulic motors 9, 9xe2x80x2 are changed among the three levels. Therefore, the cost of hydraulic equipment is reduced, and the hydraulic equipment can be installed in a limited space. And, the vehicle performance can be improved because the hydraulic pumps and the hydraulic motors can be used under the conditions efficient for the pressures and capacities of the hydraulic pump and the hydraulic motor.
A sixth invention relates to the fifth invention, wherein the speed switching means switches the rotation speed to
a first rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a maximum capacity position, and the rotation speeds of the left and right rotating bodies become a minimum speed;
a second rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a middle capacity position, and the rotation speeds of the left and right rotating bodies become a middle speed; and
a third rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a minimum capacity position, and the rotation speeds of the left and right rotating bodies become a maximum speed; and
automatically switches between the first rotation speed and the second rotation speed.
According to the sixth invention, a difference of the number of rotations between the left and right rotating bodies 100, 100xe2x80x2 can be eliminated when the rotation speeds of the left and right rotating bodies 100, 100xe2x80x2 are switched among the three levels by using the hydraulic motors 9, 9xe2x80x2 in the same way as the fifth invention.
Besides, according to the sixth invention, the switching between the first rotation speed and the second rotation speed is made automatically. The range between the first rotation speed and the second rotation speed is a work area of a low rotation speed with high torque. According to a seventh invention, the manual speed change in the work region requiring torque is unnecessary, and the operability in the work region can be improved.
The seventh invention relates to the fifth invention, wherein the speed switching means switches the rotational speed to:
a first rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a maximum capacity position, and the rotation speeds of the left and right rotating bodies become a minimum speed;
a second rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a middle capacity position, and the rotation speeds of the left and right rotating bodies become a middle speed; and
a third rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a minimum capacity position, and the rotation speeds of the left and right rotating bodies become a maximum speed; and
automatically switches between the second rotation speed and the third rotation speed.
According to the seventh invention, a difference of the number of rotations between the left and right rotating bodies 100, 100xe2x80x2 can be eliminated when the rotation speeds of the left and right rotating bodies 100, 100xe2x80x2 are switched among the three levels by the hydraulic motors 9, 9xe2x80x2 in the same way as the fifth invention.
Besides, the second rotation speed and the third rotation speed are switched automatically according to the seventh invention. The range between the second rotation speed and the third rotation speed is a running region of the high rotation speed with low torque. According to the third invention, the manual speed change in the running region requiring the rotation speed is unnecessary, and the operability in the running region can be improved.
An eighth invention relates to the fifth invention, wherein the speed switching means switches the rotation speed to:
a first rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a maximum capacity position, and the rotation speeds of the left and right rotating bodies become a minimum speed;
a second rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a middle capacity position, and the rotation speeds of the left and right rotating bodies become a middle speed; and
a third rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a minimum capacity position, and the rotation speeds of the left and right rotating bodies become a maximum speed; and
manually switches among the first rotation speed, the second rotation speed and the third rotation speed.
According to the eighth invention, a difference of the number of rotations between the left and right rotating bodies 100, 100xe2x80x2 can be eliminated when the rotation speeds of the left and right rotating bodies 100, 100xe2x80x2 are switched among the three levels by using the hydraulic motors 9, 9xe2x80x2 in the same way as the fifth invention.
Besides, the switching among the first rotation speed, the second rotation speed and the third rotation speed is made manually according to the eighth invention. According to a ninth invention, when it is not desirable to automatically switch the capacity of the hydraulic motor, the switching can be effected manually as desired.
A ninth invention relates to the fifth invention, wherein the speed switching means switches the rotational speed to:
a first rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a maximum capacity position, and the rotation speeds of the left and right rotating bodies become a minimum speed;
a second rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a middle capacity position, and the rotation speeds of the left and right rotating bodies become a middle speed; and
a third rotation speed at which the capacity positions of the left and right variable displacement hydraulic motors (9), (9xe2x80x2) become a minimum capacity position, and the rotation speeds of the left and right rotating bodies become the maximum speed; and
selects either automatic switching between the first rotation speed and the second rotation speed or automatic switching between the second rotation speed and the third rotation speed.
According to the ninth invention, a difference of the number of rotations between the left and right rotating bodies 100, 100xe2x80x2 can be eliminated when the rotation speeds of the left and right rotating bodies 100, 100xe2x80x2 are switched among the three levels by using the hydraulic motors 9, 9xe2x80x2 in the same way as the fifth invention.
Besides, the selection can be made between the automatic switching between the first rotation speed and the second rotation speed and the automatic switching between the second rotation speed and the third rotation speed. The range between the first rotation speed and the second rotation speed is a work area of a low rotation speed with high torque. The range between the second rotation speed and the third rotation speed is a running area of a high rotation speed with low torque. According to a tenth invention, when the automatic speed change in the work area is selected depending on the use conditions of the hydraulic motor, the operability in the work area can be enhanced, and the speed change in the running area can be manually made as desired. When the automatic speed change in the running area is selected depending on the use conditions of the hydraulic motor, the operability in the running area is enhanced, and the speed change in the work area is manually made as desired.
In order to achieve the third object, a tenth invention is a positioning device for changing a position of a subject to be positioned depending on a moved position of a piston (11), which comprises:
the piston (11) which moves between both stroke end positions to change the position of the subject to be positioned from a minimum position to a maximum position;
one or two or more restricting members (12, 67) which are positioned at one or two or more middle positions between both the stroke end positions to restrict the movement of the piston (11) at one or two or more middle positions; and
position control means which changes the position of the subject to be positioned among three or more positions by the piston (11) and the restricting members (12, 67).
The tenth invention will be described with reference to FIG. 16 and FIG. 17(d). The piston 11 moves between the stroke end position shown in FIG. 17(a) and the stroke end position shown in FIG. 17(d). The first piston 11 moves between both the stroke end positions to change the position of the subject to be positioned from the maximum position to the minimum position.
The third piston 67 is positioned at a first middle position as shown in FIG. 17(b), and the second piston 12 is positioned at a second middle position as shown in FIG. 17(c). When the first piston 11 comes in contact with the third piston 67, the movement of the first piston 11 is restricted at the first middle position, and when the first piston 11 comes in contact with the second piston 12, the movement of the first piston 11 is restricted by the second middle position.
The first piston 11, the second piston 12 and the third piston 67 are discontinuously positioned at the respective positions.
In other words, when the first piston 11 is positioned at one stroke end position as shown in 17(a), the position of the subject to be positioned becomes the maximum position.
When the third piston 67 is positioned at the first middle position and the first piston 11 is positioned to come in contact with the third piston 67 as shown in FIG. 17(b), the position of the subject to be positioned becomes the first middle position.
When the second piston 12 is positioned at the second middle position and the first piston 11 is positioned to come in contact with the second piston 12 as shown in FIG. 17(c), the position of the subject to be positioned becomes the second middle position.
When the first piston 11 is positioned at the other stroke end position as shown in FIG. 17(d), the position of the subject to be positioned becomes the minimum position.
According to the tenth invention, the position of the subject to be positioned can be changed among three or more positions by discontinuously positioning the first piston 11, the second piston 12 and the third piston 67 at the respective positions. Therefore, the subject to be positioned can be positioned among three or more levels by a simple structure and simple control without using a complex structure such as a servo valve and complex control. The hydraulic equipment such as the hydraulic pump can be made small in size because the number of positioning by the positioning device increases to three or more.
To achieve the third object, an eleventh invention is a speed changing device of rotating bodies using a hydraulic motor, comprising a variable displacement hydraulic motor (9) which rotatably drives the rotating bodies; a hydraulic pump (3) which supplies pressure oil to the variable displacement hydraulic motor (9); and speed switching means which changes rotation speeds of the rotating bodies by changing a capacity position of the variable displacement hydraulic motor (9), wherein the speed switching means includes:
a piston (11) which changes the capacity position of the variable displacement hydraulic motor (9) from a minimum capacity position to a maximum capacity position by moving between both stroke end positions;
one or two or more restricting members (12, 67) which restrict the movement of the piston (11) at one or two or more middle positions by being positioned at one or two or more middle positions between both the stroke end positions; and
position control means which changes the rotation speeds of the rotating bodies among three or more levels by the piston (11) and the restricting members (12, 67).
The eleventh invention will be specifically described with reference to FIG. 17.
The first piston 11 moves between the stroke end position shown in FIG. 17(a) and the stroke end position shown in FIG. 17(d). With the movement of the first piston 11 between both stroke end positions, the capacity position of the variable displacement hydraulic motor 9 varies from the maximum capacity position to the minimum capacity position.
The third piston 67 is positioned at the first middle position as shown in FIG. 17(b), and the second piston 12 is positioned at the second middle position as shown in FIG. 17(c). When the first piston 11 comes in contact with the third piston 67, the movement of the first piston 11 is restricted at the first middle position, and when the first piston 11 comes in contact with the second piston 12, the movement of the first piston 11 is restricted at the second middle position.
The first piston 11, the second piston 12 and the third piston 67 are discontinuously positioned at the respective positions.
In other words, when the first piston 11 is positioned at one stroke end position as shown in FIG. 17(a), the capacity position of the variable displacement hydraulic motor 9 becomes the maximum capacity position, and the rotation speed of the rotating body becomes the minimum speed.
And, when the third piston 67 is positioned at the first middle position and the first piston 11 is positioned to come in contact with the third piston 67 as shown in FIG. 17(b), the capacity position of the variable displacement hydraulic motor 9 becomes the first middle capacity position, and the rotation speed of the rotating body becomes the first middle speed.
And, when the second piston 12 is positioned at the second middle position and the first piston 11 is positioned to come in contact with the second piston 12 as shown in FIG. 17(c), the capacity position of the variable displacement hydraulic motor 9 becomes the second middle capacity position, and the rotation speed of the rotating body becomes the second middle speed.
And, when the first piston 11 is positioned at the other stroke end position as shown in FIG. 17(d), the capacity position of the variable displacement hydraulic motor 9 becomes the minimum capacity position, and the rotation speed of the rotating body becomes the maximum speed.
According to the eleventh invention, the rotation speeds of the rotating bodies can be switched among three or more speeds by discontinuously positioning the first piston 11, the second piston 12 and the third piston 67 at the respective positions. Therefore, the rotation speed of the hydraulic motor can be changed among three or more levels by a simple structure and simple control without using a complex structure such as a servo valve and complex control.
Because the number of speed changes of the hydraulic motor is increased to three or more levels, a maximum discharge amount of the hydraulic pump can be made small, and the hydraulic pump can be made small in size.
A twelfth invention relates to the eleventh invention, wherein the position control means comprises:
respective pressure-receiving chambers (13, 14, 15, 68) which apply the pressure oil to the piston (11) and the one or two or more restricting members (12, 67); and
pressure oil supply means which previously determines combinations of high and low pressures of the pressure oil supplied to the respective pressure-receiving chambers (13, 14, 15, 68) for the respective rotation speeds of the rotating bodies and supplies the pressure oil having the combinations of high and low pressures corresponding to the rotation speed to be changed to the pressure-receiving chambers (13, 14, 15, 68) respectively.
The twelfth invention will be described with reference to FIG. 17 and FIG. 18.
The first piston 11, the second piston 12 and the third piston 67 are moved when the pressure oil acts on the pressure-receiving chambers 13, 14, 15, 68.
As shown in FIG. 18, the combinations of high and low (ON, OFF) pressures of the pressure oil supplied to the respective pressure-receiving chambers 13, 14, 15, 68 are previously determined for each rotation speed of the rotating body. When the pressure oils having the combinations of the high and low pressures corresponding to the rotation speed to be changed are supplied to the respective pressure-receiving chambers 13, 14, 15, 68, the first piston 11, the second piston 12 and the third piston 67 are discontinuously positioned, and the rotation speed of the rotating body is changed.
According to the twelfth invention, the pressure oils having the combination of high and low pressures corresponding to the rotation speed to which the speed is changed are supplied to the respective pressure-receiving chambers 13, 14, 15, 68 to discontinuously position the first piston 11, the second piston 12 and the third piston 67, so that the hydraulic motor structure and control can be facilitated further more.